The Irish hare is traditionally considered a subspecies of mountain hare. However, it may be genetically distinct enough to be considered to be a unique species. Despite its uniqueness, its genetic integrity is being eroded through hybridization with the European hare, an introduced species. This species also is outcompeting the Irish hare with which it shares an ecological niche.

Invasive species are known to cause lots of problems on islands. Islands are a major force for speciation, for island populations are quite subject to founder effect genetic drift. When one realizes that islands may have very different selection pressures from continental populations, organisms on islands can evolve quite differently from their mainland relatives.

Further, because islands are quite finite compared to the larger continents in terms of the resources available, these insular species often adapt to the most novel niches. My favorite example are the marine iguanas of the Galapagos, which warm themselves on volcanic rocks, then crawl down into the surf to eat seaweed. Although there were once fully aquatic monitor lizards known as Mosasaurs, they were predators. I know of no other herbivorous lizard that has taken to the sea in this fashion. It is thought that these iguanas derive from land foraging iguanas that were marooned on a sinking island with very little vegetation for forage. They were able to survive by eating seaweed, which could only be accessed by entering the ocean.

However, just as islands can play a role in creating species, the species they help create may be more ecologically sensitive to invasive species. In general, the more isolated the island, the more problems invasive species cause. The New Zealand archipelago is perhaps the most isolated landmass on earth, and it has been for 80 million years. It has no native land mammals, except several species of bat. That’s right. With the exception of bats, all the land mammals on New Zealand have been introduced. Polynesian rats, pigs, and dogs were introduced by the Polynesians. All the rest come from the British Empire.

During those 80 million years, New Zealand became the islands of birds. Birds evolved to fill mammalian niches, and some of those birds evolved rather esoteric and peculiar reproductive strategies, which actually are quite inefficient (see the kakapo). If you don’t suffer much predation, one never needs to evolve efficient reproductive strategies. Of course, when animals like these experience modest predation pressures, their populations wind up collapsing.

Of course, the islands of New Zealand are an extreme example, but even islands that don’t have the long periods of isolation can have these problems.

Even Ireland.

Ireland has been connected to the neighboring island of Great Britain and to the European mainland at several times during its relatively recent geologic history. Ireland had wolves, brown bears, and Eurasian lynx, which are the same large predators that once roamed virtually the whole of the Eurasian continent. Of course, these animals are now extinct, but much of Ireland’s wildlife is broadly shared with Great Britain and Northern Europe. In fact, the stoats that live in Ireland now descend from ones that were there during the last Ice Age.

Ireland also has its own unique subspecies of wood mouse and pygmy shrew.

And it is these two species that have declined significantly once the bank vole and greater white-toothed shrew were introduced.

Science Daily reports that Ireland’s unique fauna may not be holding up so well when faced with introduced competitors:

The red squirrel, Irish hare and red deer are just some of Ireland’s indigenous species which are under threat as a result of the introduction of foreign species. A new study which took place over the last two years looked at the impact of two introduced species — the bank vole and greater white toothed shrew — on two native small mammals, the wood mouse and the pygmy shrew. If the rate of invasion continues as at present throughout the island of Ireland, its native small mammals will die out in at least 80 per cent of their available habitat.

The study, published in the international journal Biological Invasions, found that in the recent past the pygmy shrew has completely vanished in parts of Ireland where both invasive small mammals are found. Wood mouse numbers have decreased by more than 50 per cent in areas where the bank vole is longest established.

Small mammals occupy central positions in food webs, so major changes in species composition which are already occurring, will have both top-down and bottom-up effects in the ecosystem affecting bird and mammal predators as well as the invertebrates, seeds and seedling that small rodents and insectivores feed on.

Professor Ian Montgomery, lead researcher from the School of Biological Sciences at Queen’s University, said: “The introduction of alien mammals to Ireland over the last 100 years has had major detrimental effects, threatening our indigenous habitats and species. The American grey squirrel, for example, passes a deadly virus to native red squirrels, whilst European hares threaten the ecological and genetic integrity of the native Irish hare through competition and interbreeding.

“Governments, both north and south of the border, are urged to work together to address the overall problem of invasive mammals throughout Ireland, and ensure that we understand both the mechanisms of invasion and the impacts of these aliens. It is no longer tenable to treat each invasive species as an isolated case. We should establish a realistic plan identifying the mammal species that are key to maintaining our unique biodiversity and ecology and those that we should eliminate or control.”

The new study is the first of its kind to systematically analyse the cumulative effects of invasive mammal species on indigenous species. Such a process is known as ‘invasional meltdown’.

Ireland is not a particularly isolated island.

Inhabitants of Ireland always traded with those of Great Britain, who in turn traded with those of France, Northern Europe, and Scandinavia. Through human history, it’s never been fully isolated from trade, and trade brings in all sorts of different species.

But it is amazing how fragile some of Ireland’s species are when it comes to competition from invasive species.

And if an island as connected to the Eurasian mainland as Ireland can suffer from invasive species from Great Britain and the continent, just imagine how severely affected organisms on more isolated islands from invasives.

Islands produce many unique species through the very nature of islands.

However, it is because of the very nature of islands that these species are often quite fragile

Like this:

This painting is marketed as “Landseer Newfoundland” by Edmund Bristow.

I cannot find the date for the painting, but it is unlikely that this was the original title.

The simple reason is that Bristow was a contemporary of Landseer, and the black and white large Newfoundlands didn’t get that name until some time later.

Newfoundland dogs of various types were known for their retrieving prowess. The big Newfoundland, sometimes call the “Large Labrador,” was capable of retrieving quite well. Its exact origins are not clear. It is even unclear if the dog existed in this form in Newfoundland itself or if this dog is nothing more than a European improvement upon the native water dog of Newfoundland.

I think the bulk of the evidence suggests the latter, but I could be wrong.

Matt Walker of the BBC writes about a very interesting paper in the journal Evolutionthat discusses why animals have not been able to evolve against human predators. Predators and prey are normally locked in an evolutionary arms race in which predation places selection pressures upon prey to evolve defenses. The two most common ways that prey species evolve defenses against predation are to grow really big or produce toxins, but neither of these are particularly good defenses against human predators:

“The spread of modern humans represents one of the great ecological and evolutionary transformations in the history of life,” Prof [Geerat] Vermeij writes in Evolution.

We hunted and gathered on land, but soon began exploiting intertidal zones, taking shellfish and fish. Such intertidal zones were important food sources for prehistoric human populations living in places as far and wide as South America, South Africa, California and Oceania.

Then we started taking big animals. When we did the very adaptations that offered protection against natural predators attracted rather than deterred human hunters. The huge size of mammals such as bison or whales made them juicy targets for meat-hungry humans for example.

Other defensive ornaments became disadvantageous as humans evolved into super-predators. Elephants were killed for ivory, crabs and lobsters fished for their large meaty claws. These once advantageous traits became liabilities in the modern, human-dominated world.

We didn’t just take large species, we also preferentially harvested out the largest individuals of smaller species, a problem that persists today.

Prof Vermeij has examined the degree to which this happens.

He looked at one group of animals, marine molluscs and echinoderms such as starfish, and surveyed all the scientific research into how they have been exploited by humans. We select the largest individuals among 35 of 40 species studied, he discovered.

That means that size is no longer a refuge. Whereas growing big may have been one defence against natural predators, it offers no defence against human super-predators.

Sticking to rocks, as limpets do, is no good either as humans have invented picks and knives to prise them off.

Prey animals may do better to become toxic instead, and there is evidence that some marine species have become poisonous to people, either producing their own toxins, or by harnessing toxins produced by microbes. Reef fish and crabs are often toxic to people because they contain unpalatable, and sometimes lethal, dinoflagellates, for example.

But humans have found ways to get around this too. Many toxins need to be concentrated into organs such as the liver. And humans have learnt to remove these, to avoid their ill effects.

In short the way humans hunt appears to be the main factor preventing animals evolving adaptations to defend themselves from us.

Animals do respond to selective pressures, even over short time scales, and many species have responded to humans being super-predators, says Prof Vermeij.

By eliminating large apex predators, secondary predators have boomed. As cod numbers crashed in the 20th Century, their place was taken by an abundance of shrimp, lobster and crabs, which in turn feed on marine snails. As a result, these snails may have evolved thicker shells to protect themselves against these marauding shell-crunching crustaceans.

But we hunt on too grand a scale, with too much ingenuity, targeting the biggest animals.

“Our arrival and technological history has engendered an enormous change in the evolution of most species on Earth,” says Prof Vermeij.

In evolutionary terms, we leave our prey with nowhere to go. They have no way to defend themselves and simply cannot respond.

And that, says Prof Vermeij, represents a cataclysmic shift for species on this planet, the implications of which, he adds, we have barely begun to understand.

I have long wondered why predation by humans is not considered more carefully in our discussions about evolution.

I have often thought that the reason why people have such a hard time taming wolves now and may not have had such problems in the past is that wolves experienced an unbelievable selection pressure in the form of human persecution. When wolves became too wary to kill with weapons, we resorted to poisons and traps, and all of these pressures left behind only the most “paranoid” and reactive individuals to pass on their genes. This might go a long way to explaining why it was so easy for ancient man to tame wolves, but it is now quite difficult for us to do so. And even if we wind up having a wolf that is imprinted upon humans, the chances of it being more like a friendly and docile dog are very low. However, there are and were wolves like this in modern times– Wags and Romeo are good examples.

I’ve also wondered about the behavior of white-tailed deer when they see me approach. I am from the only species that can kill a deer as soon as I get a good clear view of it. No other animal that can kill a deer can do that. All the rest– be they bobcats or coyotes– most put their teeth on the flesh. So when a deer sees me approach, it must know that the threat is that much more than if it sees a pack of coyotes approaching at the same distance.

I’ve also wondered about the way squirrels run away from people. They always try to stay on the opposite side of the trunk from where a person is standing. Any other animal that would pursue a squirrel into the trees– like a fisher or marten (which used to be found here)–would follow the squirrel course almost exactly. It would have no reason to try keep itself on the other side of the trunk. Such behavior would have some advantage against raptors, but raptors would come down on the squirrel. The threat from a human hunter would come from the other direction. Somewhere along the line, they evolved this strategy to avoid being shot.

The behavior of ruffed grouse has also changed dramatically as the result of human hunting.William Harnden Foster wrote the first important treatise on sport hunting ruffed grouse in New England, simply entitled New England Grouse Shooting. Writing in the early twentieth century, Foster discusses the evolution of ruffed grouse behavior in response to rapacious market hunting. Market hunting was always a major threat to American wildlife, and although today we like to castigate Africans for their “bushmeat” trade, it was actually perfected in America. As Americans gained more wealth as a result of our industrial revolution, they came to want wild game meat. Fine restaurants and markets in major cities offered the flesh of all sorts of wild animals, and many species, including white-tailed deer and Eastern wild turkeys nearly became extinct through this early American bushmeat trade. Grouse were always in demand for the table, and in the early days, they were easily killed. Ruffed grouse apparently originally lived in small flocks, and when a dog flushed them, the whole flock took refuge in a tree, where a hunter could easily pick them off with his fowling piece. Over time, this selection pressure left behind only grouse that took off and flew greater distances from where they were flushed. And it also made the grouse much more solitary. Today, it is very rare to find more than one grouse in the same spot, unless it is a hen and her poults.

In no case has these animals evolved a very effective defense against human predators. So long as we have guns, we can get them.

We’ve even been able to kill the largest whales very effectively. In the later days of whaling in Newfoundland and the Maritimes, the blue whale and the finback were rather easily subdued with harpoons that had extra blades that pojected out as soon as they main shaft lodged itself in the whale’s flesh. These extra blades caused the whale to bleed out and die more rapidly. All the whalers needed was a strong cord connected to the harpoon and a very stout boat to wait it out.

It is only now that we’re beginning to realize what human predation is actually doing to the evolution of animals and to the ecosystems in which they inhabit.